(a) Technical Field
The present disclosure relates to a liquid crystal display.
(b) Discussion of the Related Art
A liquid crystal display includes two display panels provided with field generating electrodes and a liquid crystal layer disposed between the two panels. The field generating electrodes may include a plurality of pixel electrodes and a common electrode. Voltages are applied to the field generating electrodes to generate an electric field in the liquid crystal layer. The electric field determines the orientation of liquid crystal molecules of the liquid crystal layer. These molecular orientations in turn determine the transmittance of light passing through the liquid crystal layer, thereby displaying an image by controlling polarization of incident light.
The liquid crystal display also includes a switching element that is connected to each pixel electrode and a plurality of signal lines which include gate and data lines. A voltage may be applied to each pixel electrode through the gate and data lines by controlling the switching element.
A liquid crystal display with a vertically aligned mode has a long axis of liquid crystal molecules arranged perpendicular to a vertical display panel. When an electric field is not applied, the liquid crystal display has a large contrast ratio and a wide reference viewing angle. An example of a wide reference viewing angle is a viewing angle in which a contrast ratio is 1:10.
A wide viewing angle in a liquid crystal display with a vertical alignment mode may be produced by forming a cutout and a protrusion on a field generating electrode.
Since an inclination direction of a liquid crystal molecule can be determined by a cutout and a protrusion, a reference viewing angle can be enlarged by distributing an inclination direction of the liquid crystal molecule in several directions when the cutouts and/or protrusions are used.
Side visibility is improved by a method of adjusting transmittance by changing a voltage of two subpixels by directly applying a voltage to one subpixel and dropping a voltage through capacitive coupling in the other subpixel after dividing one pixel into two subpixels and coupling two subpixels through capacitive coupling.
However, in this method, transmittance of the two subpixels cannot be accurately adjusted to a desired level, and light transmittance changes depending on a particular color. Further, the aperture ratio deteriorates due to the addition of a conductor for capacitive coupling, and transmittance decreases due to a voltage drop by the capacitive coupling. Moreover, because it is difficult to transmit light in a part with a protrusion or a cutout, the aperture ratio deteriorates further as the number of protrusions or cutouts increases.
It has been suggested that aperture ratio may be increased by use of an ultra-high aperture ratio structure that enlarges a pixel electrode. However, a strong lateral field is generated around the edge of a pixel electrode because a distance between pixel electrodes is short and a distance between a pixel electrode and a data line is also short. Alignment of liquid crystal molecules is distributed due to such a lateral field, whereby texture or light leakage is generated and response time is delayed.
Furthermore, a liquid crystal display with a vertically aligned mode has lower side visibility than front visibility. For example, in a liquid crystal display of a PVA (patterned vertically aligned) mode with a cutout, an image becomes bright towards the side, and in a serious case, a picture distorted because there is no luminance difference between high grays.
There is a need for a liquid crystal display with improved transmittance, aperture ratio, and side visibility.